One of them believes the publication of his report, which catalogues the unprecedented rate of ice melt in the Arctic, was delayed as Americans prepared to vote in 2004.

The scientists claim that when Bush came to power in 2000 his administration selected advice which argued that global warming was not a result of human activities and that the phenomenon could be natural.

WHAT PANORAMA FOUND OUT

For five or 10 years the public has not been fully informed. We were not taking the initial steps that need to be taken. If we continue down this path we're going to be past a point at which we can avoid really large climate changes.

Jim HansenUS climate scientist

If the report had come out it would have been a very strong piece in the presidential election in the US.

Bob CorellAuthor of Arctic Assessment Report

If they could suppress it they would. If they couldn't they would ignore it. If they could edit it they would edit it.

Former government official

But one of the people who suggested the president adopt that position explains to Panorama how he has changed his point of view: "It's now 2006. I think most people would conclude that there is global warming taking place and that the behaviour of humans is affecting the climate. I am not the administration. What they want to do is their business. it has nothing to do with what I believe."

Panorama's reporter Hilary Andersson visits some of the first refugees of global warming who come from an island in Arctic Alaska which has been inhabited for 4,000 years ago but is now melting into the sea.

In the last six years most industrialised nations have cut greenhouse gas emissions but under Bush America's emissions have increased by an average of one per cent a year.

The administration is now spending money to establish cleaner ways of burning coal and to cut emissions but is still reluctant to risk damaging the American fuel industries.

I told the world I thought the Kyoto deal was a lousy deal for America. It meant that we had to cut emissions below 1990 levels which would have meant I would have presided over massive lay offs and economic destruction.

President George W Bush

Energy is central to our economy. If you're going to make energy policy you need to talk to the energy industry.

James ConnaughtonBush's senior adviser on the environment

But some scientists say this will take too long. One of them tells Panorama how he was told NASA would have to approve everything he planned to write and say publicly about the effects of global warming.

Another scientist from the National Oceanic and Atmospheric Administration (NOAA) tells Panorama he had research which established global warming could increase the intensity of hurricanes. He was due to give an interview about his work but claims he was gagged.

Three weeks later in August 2005, Hurricane Katrina killed at least 1,200 people in New Orleans and was recorded as one of the strongest Atlantic storms. But the NOAA website said unusual hurricane activity is not related to global warming.

Panorama learns that some scientists are afraid that what they see as a cover up will leave it too late for the US to have any hope of controlling climate changes brought about by global warming.

Panorama: Climate chaos: Bush's climate of Fear was on BBC One on June 6 2006.